1. Field of the Invention
This invention relates to variable speed power transmission mechanisms and has particular reference to a quick-change variable speed gearing attachment for driving the workpiece cutting tool of a lathe or similar machining apparatus.
2. Description of the Prior Art
Although many lathes incorporate built-in quick-change variable speed gearing devices for power driving a cutting tool relative to a workpiece for both general cutting or for cutting screw thread, many others, particularly those in the small and inexpensive categories such as are used for hobby and model making, do not. Attachments are available which can be mounted on such lathes for screw threading and the like but they generally require special gears and other elements for each rate of feed of the tool carriage. Thus, in order to cut various ores of different screw threads or to move the cutting tool at different rates for general cutting operations, a large number of different gears or other elements must be carried on hand and a certain amount of dismantling and reassembly as well as adjustment of the lathe must generally be performed each time a change in feed rate is to be made. This is not only expensive but, to change from one to another set up is generally tedious, time consuming and subject to error.